The present invention relates to an airbag and an airbag system for use in automobiles and so forth.
It is known to provide a driver-seat airbag system to a steering wheel and a passenger airbag system to an instrument panel in front of a passenger seat to restrain the occupants of an automobile in a collision.
As an airbag system that receives the arms of an occupant with an airbag to restrain the occupant in a collision, an airbag system having a driver-seat airbag and arm bags disposed on the right and left of the lower part of the driver-seat airbag is disclosed in Japanese Unexamined Patent Application Publication No. 2003-182500. However, the airbag system uses three airbags in total, so that it may increase in cost.
One example is an airbag formed of two front and rear panels. FIGS. 11 to 18 of Japanese Unexamined Patent Application Publication No. 2000-25544 describe an airbag having a large thickness in an inflated state and a procedure for sewing it. The airbag and its sewing procedure will now be described with reference to FIGS. 4 to 11 disclosed in the attached drawings of the specification.
According to claim 2 of the reference,
“An airbag comprising two substantially trapezoidal panels A and B sewn together, wherein the panel A has a side 2 corresponding to the upper side of the trapezoid, a side 4 corresponding to the bottom of the trapezoid, and sides 1 and 3, corresponding to the hypotenuses of the trapezoid, the side 4 having a rectangular cut 5 in the center;
the panel B has a side 12 corresponding to the upper side of the trapezoid, a side 14 corresponding to the bottom of the trapezoid, and sides 11 and 13 corresponding to the two hypotenuses of the trapezoid, the side 14 having a rectangular projection 15 in the center;
the projection 15 having sides 15a and 15b continuing to the side 14, and a side 15c connecting the sides 15a and 15b, the side 1 of the panel A having a side if overlapping the side 11 of the panel B and a side 1r extending therefrom;
the side 3 of the panel A having a side 3f overlapping the side 13 of the panel B and a side 3r extending therefrom;
the side 4 of the panel A having sides 4a and 4b on both sides of the rectangular cut 5;
the rectangular cut 5 having sides 51 and 53 continuing to the sides 4a and 4b and a side 52 connecting the sides 51 and 53;
the side 14 of the panel B having sides 14a and 14b between the both sides 15a and 15b of the projection 15 and the sides 11 and 13;
the panels A and B being sewn with a seam 20 along the sides 1f and 11, the sides 2 and 12, and the sides 3f and 13;
the part along the side 4a and the part along the side 4b of the panel A being sewn up with a seam 30;
the part along the side 15a and the part along the side 14a of the panel B being sewn with a seam 58;
the part along the side 15b of the panel A and the part along the side 14b of the panel B being sewn with the seam 58;
the part along the sides 1r and 3r of the panel A and the part along the side 15c of the panel B being sewn up with a seam 48;
the part along the sides 51 and 53 of the rectangular cut 5 and the part along the side 52 of the panel A being sewn with a seam 60.”
To manufacture the airbag, as shown in FIGS. 4(a) and 4(b), the two panels A and B are cut from a base fabric and placed one on another. The panel A has the shape of an approximate trapezoid having four sides 1, 2, 3, and 4. The side 4 corresponding to the bottom of the trapezoid is curved in substantially elbow shape, in the center of which the rectangular cut ′5 is provided. The side 4 of the panel A has sides 4a and 4b on both sides of the rectangular cut 5. The rectangular cut 5 has sides 51 and 53 that continue to the sides 4b and 4a, respectively, and a side 52 that connects the sides 51 and 53.
The sides 1 and 3 corresponding to the hypotenuses of the trapezoid have front sides if and 3f and rear sides 1r and 3r, respectively. The sides lf and 3f are substantially equal in length to the sides 11 and 13.
The panel A has a gas port 9.
The panel B has the shape of an approximate trapezoid having four sides 11, 12, 13, and 14. The side 14 corresponding to the bottom of the trapezoid has a projection 15. Reference numerals 15a and 15b indicate sides continuing to the side 14 of the projection 15. Numeral 15 denotes a side connecting the sides 15a and 15b. Numerals 14a and 14b indicate parts of the side 14 extending to both sides of the projection 15.
The panels A and B have been put one on the other such that the sides if and 11, the sides 2f and 12, and the sides 3f and 13 correspond to each other, and are sewn along the sides 1 to 3 and 11 to 13, as shown in FIGS. 4(c) and 4(d). Numeral 20 indicates a seam thereof. The sides 1r and 3r extend over the sides 11 and 13, respectively, so that they are not sewn to the sides 11 and 13. FIG. 4(d) is a cross sectional view taken along line D-D of FIG. 4(c).
The panels A and B of the sewn body are drawn along the arrow G of FIG. 4(d).
Thus, as shown in FIGS. 5(a) and 6, the panel A is folded in two along the center line g in FIG. 4(c), so that the sides 4a and 4b overlap with each other. The panel B is also folded in two along the center line g, and the projection 15 is also folded in two, so that the sides 15a and 15b overlap with each other, and also the sides 14a and 14b overlap with each other. Then, as shown in FIGS. 5(b) and 7, the parts of the panel A along the sides 4a and 4b are sewn up. Numeral 30 indicates a seam along the sides 4a and 4b. 
FIG. 5(c) is a cross-sectional view taken along line 5(c)-5(c) of FIG. 5(b); FIG. 5(d) is a cross-sectional view taken along arrow 5(d)-5(d) of FIG. 5(b).
As shown in FIG. 5(c), the sewing portions 21 with the seam 20 are disposed outside the bag.
The panels A and B of the sewn bag are drawn along arrows E in FIG. 5(d) and as such, are brought into the state shown in FIG. 5(e). They are further drawn along arrows F in FIG. 5(e) into the state shown in FIGS. 5(f) and 8, in which the sides 1r and 3r of the panel A are brought into a straight line.
As shown in FIGS. 9 and 11, the side 15c of the projection 15 is sewn on the sides 1r and 3r of the panel A with a seam 48, and the sides 15a and 14a and the sides 15b and 14b are sewn with a seam 58, respectively.
Subsequently, as shown in FIG. 10(a), the left and right corners 5L and SR of the rectangular cut 5, at which the sides 52 and 51, and the sides 52 and 53 intersect, respectively, are drawn along arrows XB. As shown in FIG. 10(b), the panel A is then sewn along the sides 51, 52, and 53. Numeral 60 indicates a seam thereof.
Thus, the airbag shown in FIG. 11 is completed.
Accordingly, it is an object of the present invention to provide an airbag capable of receiving occupant's arms at low cost.